Four square test device with torque stabilization

ABSTRACT

A test device using the &#39;&#39;&#39;&#39;four square&#39;&#39;&#39;&#39; principal of testing specimens which permits input of dynamic torque changes and being arranged to eliminate the inertia effects of the mass of connecting gears or mechanisms between the parallel members of the four square test device.

United States Patent Petersen 1 Sept. 12, 1972 [54] FOUR SQUARE TESTDEVICE WITH TORQUE STABILIZATION [72] Inventor: Niel R. Petersen,Hopkins, Minn. [73] Assignee: MTS Systems Corporation, Minneapolis,Minn. [22] Filed: Dec. 31, 1970 21 1 Appl. No.2 103,063

[52] US. Cl..... ..73/162, 73/99 [51] Int. Cl ..G0lm 13/02 [58] Field ofSearch ..73/99, 162

[56] References Cited UNITED STATES PATENTS 3,112,643 12/1963 Lanahan..73/99 X 5/1960 Shipley ..73/162X 4/1961 Livezey ..73/162 PrimaryExaminer-Jerry W. Myracle Attorney-Dugger, Peterson, Johnson & Westman[57] ABSTRACT A test device using the four square principal of testingspecimens which pemiits input of dynamic torque. changes and beingarranged to eliminate the inertia effects of the mass of connectinggears or mechanisms between the parallel members of the four square testdevice.

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N/EL R. PETERSEN w wzwm BACKGROUND OF THE INVENTION 1. Field of theInvention The present invention relates to testing devices utilizing thefour square principle and wherein dynamic torque input on the testspeciman can be provided without introducing undesirable inertiaeffects.

2. Prior Art Four square test devicesare commonly known, and comprise asystem where generally four substantially identical specimens, usually.shafts or axles, are tested in; a system. The shafts are connected intopairs, and each pair comprises two shafts connected in series withuniversal joints or the like, and mounted on suitable hearings. Thepairs of shafts are arranged in side by side relationship, and havefirst and second ends. At their ends, one pair of shafts is connected tothe other pair with chains or gears so that the shafts can be torqueloaded against each other. The torque in one pair of shafts is opposedby the torque in the other-pair of shafts through the gears. Then theshafts are driven at one end with a motor. The amount of torque in theshafts of course depends upon the position of the gears.

It is also known to introduce dynamicv torques into this type of testsystem through the use of an actuator acting on one of the sides of thesystem only, and this increase or decrease in torque had to act throughthe connecting gears on'the opposite end of the series coupled specimento be transmitted into the parallel specimens. The connectingdevices'have a mass, and when large gears are used for connecting thespecimen, the mass of the gears cause inertia load problems and may beexcited into resonance, causing undesirable oscillation of the entiretestsystem. Therefore peak loads or torques are applied that are notthe; proper torques forthe program beingused with the tested device.

SUMMARY OF THE INVENTION The present invention relates to a four-squaretest device that permits the introduction of dynamic torques withouthaving the systems'subjected to resonant or inertia loads. The systemcomprises at least two specimen sets and the use of dual hydraulicactuators, one on each of the specimen sets so that changes in torque issimultaneously made through each of the actuators to therefore eliminatethe transmission of this increase of torque through gears or chains atthe opposite end of the specimen sets. This introduction of torque canbe done quickly with vane type hydraulic actuators controlled with servovalves, and additional indicators can be used to indicate the relativeangular position of the two actuators to make sure that the actuators donot bottom out.

In addition, this system utilizes load cells for indicating the actualtorque being introduced into the specimens, and the actual torque signalfrom the load cells can be compared with the preset program to makeinstantaneous torque adjustments. The advantage is that the inertia ofthe connecting gears at opposite ends of the specimen sets from thehydraulic actuators is not coupled into the test system and thereforecannot subject the sys'tem to dynamic inertia effects, which previouslyhave limited the programming of the test devices insofar as dynamictorque changes are concerned.

2 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representationof a dynamic torque applying four square test device made according tothe present invention;

FIG. 2 is a sectional view through the center of the torque input end ofthe four square test device showing the details of the typical hydraulicactuator used with the present invention;

FIG. 3 is a sectional view taken as on line 3-3 in FIG. 2; and

.FIG. 4 is a schematic representation of the test circuit and controlsused with thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 inparticular, a four square test device illustrated generally at 10comprises a first specimen 1], and a 'secondspecimen 12, which arecoupled together in series with a suitable connecting shaft 13 throughuniversal joints 14. The shaft 13 is supported with a bearing 15. Thesetwo shafts or specimens 11 and 12 could be any test shafts, such aspropeller shafts for automobiles, axles for automobiles or the like.

The first and second specimens, 1 l and 12, comprise a series connectedpair of specimens forming a specimen set in a four square testingdevice. The input ends are adjacent the outer end of the first specimen1 I, and the end of specimen l2 opposite from universal joint 14 isconnected through a universal joint 18 to a shaft 16 that is rotatablymounted on suitable bearings in a housing 17 which is supported in atest frame or on a block. The shaft 16 has a first spur gear 20 drivablymounted thereon, and this first gear 20 engages a second spur gear 21that is in turn drivably mounted onto a shaft 22 also rotatably mountedin the housing 17. The shaft 22, is connected through a universal joint23 to a third specimen 24, that comprises a specimen in series with afourth specimen 25. The specimens 24 and 25 comprise a specimen set.

The third and fourth specimens 24 and 25 are connected in series with ashaft 26 and universal joints 27 at opposite ends of the shaft 26. Theshaft 26 is also rotatably mounted on a bearing assembly 28 that is inthe center of the shaft 26 and that corresponds to bearing 15.

A drive coupling 31 is provided on the outer end of shaft 22, and anelectric drive motor of usual design indicated at 32 is utilized fordriving the specimens. The shafts 1 1 and 12 are parallel to shafts 24and 25.

At the opposite end of the unit from housing 17, there is a housing 33.Between the housing 33 and specimen 11 there is a universal joint 34,and a shaft 35 having a torque cell 36 mounted therein. The torque cell36 is of usual design which will measure the torque being transmitted bythe shaft 35, and consequently the specimens 1 1 and 12, and the cellwill deliver electrical signals proportional to the amount of torque inthe shaft 35 through suitable slip rings, conventionally known and used.

In addition, the specimen 25 has a universal joint 37 connected thereto,which is in turn connected to a shaft 38 in which a second torque cell39 is mounted. Torque cell 39 is used to measure or monitor the torquein shaft 38.

Referring to FIG. 2, it can be seen that the housing 33 has bearingswhich support the shafts 35 and 38 so that the shafts are rotatably heldin place. The housing 33 is schematically shown to be supported in atest stand or the like. The unit can all be mounted onto a common frameso that the housings l7 and 33 are in the common frame.

At this end of the test device, the amount of torque in the specimens 11and 12, and in the specimens 24 and 25 is controlled through the use oftwo rotary hydraulic actuators. The parallel shafts are coupled togetherwith drive gears so they can be rotated at varying speeds and torques.As shown, the shaft 35, which is coupled to the specimens 11 and 12, hasa vane type hydraulic actuator 42 mounted thereon inside the housing 33,and this actuator 42 has an outer housing that is rotatably mounted onthe shaft 35. The shaft 35 has an integral enlarged portion 43 on whichvanes 44 are fixedly mounted, and these mate with internal vanes 45 onthe interior of the housing 42. Vanes 44 and 45 together form fourchambers, namely chambers 46A and 46B, and 47A and 47B. The chambers 46Aand 46B are connected with a cross passage 48 in shaft 35 that in turnopens to an outwardly extending passage 49, that extends outwardly alongthe shaft 35 past the outboard bearing of the housing 33. The passage 49has a right angle turn so the passage opens to the outer surface of theshaft and to an annular chamber 55 defined in the interior of ahydraulic commutator 52.

Likewise, chambers 47A and 47B are connected with a cross passageway 53in shaft 35 that opens into a passageway 54 extending outwardly alongthe shaft 35, and then opening into a second chamber 56 in the hydrauliccommutator 52. The hydraulic commutator 52 has, as shown, the chambers55 and 56 that align with the passageways 49 and 54 as shown, and thehydraulic commutator supplies fluid under pressure from a first servovalve 57 so that the amount of pressure in the chambers 46A and B or 47Aand B can be changed. The amount of pressure therefore controls theangular movement between the vanes 44 and 45. The outer housing 42 isconnected with suitable long bolts or similar connecting devices shownat 60 to a first gear 61 that is rotatably mounted on a suitable bearing62 to the shaft 35 the teeth of the gear 61 engage the teeth of a gear63 that is also rotatably mounted with a bearing 64 on the shaft 38. Theshaft 38 is connected to specimens 24 and 25.

The gear 63 is connected with suitable bolts or connecting devices 65 toa second rotary hydraulic actuator 66 that is constructed identically tothe actuator 42, and the shaft 38 also has the vanes and chambers thatare illustratively shown in FIG. 3 in connection with the hydraulicactuator 42. The actuator 66 is also a vane type hydraulic actuatorsupplied with pressure through a-rqtary hydraulic commutator 67 at theouter end of the shaft 38. The commutator 67 is connected to a secondservo valve 68 that also receives fluid under pressure from the samesource as servo valve 57. The outer portion of the commutators remainstationary while the shafts rotate.

Thus it can be seen that the amount of torque in the specimens 11, 12and 24, 25, can be controlled by the amount of deflection between thevanes 44 and 45 of each of the hydraulic actuators 42 and 66. The amountof torque that is being transmitted through the actuators can becontrolled by the respective servo valves 57 and 68 in response tosignals from outside sources. The torque is transferred through thegears 61 and 63 to the specimens, and the gears are coupled to theshafts and loaded through the hydraulic actuators.

It is possible for the vanes of one of the actuators 42 or 66 to driftfrom a centered position so that while the proper total torque may becarried, the vanes of one of the actuators may bottom out so that thevanes 44 and 45 were contacting. In order to eliminate this potentialproblem, suitable angle transducers are placed on each of the shafts 35and 38 to sense the angular shift between the outer housings of thetorque actuators and the respective shafts with respect to a referencepoint. For example, an angle sensor 70 is positioned on shaft 35, andcomprises two parts, one of which goes along with shaft 35 and the otherwhich travels with the housing 42. This is merely a potentiometer thatchanges resistance with a change of angle from a reference position.Suitable slip rings can be used to take the signal off the shaft 35. Theslip rings are shown schematically at 71 and connections to the slipring can pass through drilled openings in the shaft 35 itself. Thesensor 70 could also be a synchro-type angle sensor if desired. Likewisean angle sensor 72 is positioned on the shaft 38 to sense the anglebetween the shaft 38 and the housing of the actuator 66 from a referencepoint and a slip ring assembly 73 can be utilized for transferring thesignal from the rotating shafts.

The test unit can be controlled as shown schematically in FIG. 4. Atorque program from a master control is indicated generally at 80, andthe command signal from this torque program can be fed into an errorsignal amplifier shown as a summing junction 81 which receives a signalthat is proportional to an average of the total signals from both thetorque cells 36 and 39, which give out their signals into a amplifier 82that gives an output signal indicating the average of the two torquecell signals. A loop gain amplifier 83 is to provide the gain for thedifferential signal between the programmed torque and the actual torqueas measured by the two load cells which forms the control signal for thesystem. This signal is sent to suitable amplifiers 84 and 85 that drivethe respective servo valves 57 and 68 to change the torque on therespective shafts by operating the actuators 42 and 46 in order to raisethe torque level as desired. It should be noted that both actuators 42and 46 are operated simultaneously, so that the torque level will bechanged by operating both actuators a preselected amount. The angle orposition signals from the transducers 70 and 71 which are represented byboxes in the control schematic, are used to feed in separate signalsinto the lines for controlling the servo valves if there is anydifference. As shown, one of the angle sensors feeds a plus signal intoamplifiers 86 and 87 and the other angle sensor 71 feeds an oppositesignal in to amplifier 86. The amplifier 86 is an averaging amplifier(K=%) so that the gain is equal to A. Any signal coming from amplifier86 is fed back to the servo valve controls so that the angle valves areadjusted for equalization of deflection. The amplifier 86 will put out azero signal when the position angles of the actuators are equal. If theactuators deflect any from equal position a signal will appear at thesumming junctions 88 and 89 to raise or lower the flow signals throughthe servo valves sufficiently to cause equal angles of deflection of therotary actuators. The angle equalization signal adds to or subtractsfrom the signal from amplifier 83. One of the summing junctions 88 or 89is aphase inverter for the angle equalization signal in order to obtainproper operation of the servo valves for angle equalization. Theamplifier 87 gives a signal that indicates total specimen deflection ata readout or indicator 9-0. Total angle deflection is used fordetermining when the specimens have reached their yield point. Synchromechanisms can also be used for angle equalization. I

Thus, for a given torque program, if the unit is operating, and I drivemotor 32 is rotating the specimens, a stepped input of torque can bemade by having the servo valves 57 and 68 actuated to increase thetorque being carried by each of the shafts 35 and 38, which torque willbe transmitted to the specimens connected thereto without going throughthe gears and 21. This eliminates the inertial effect of the gears 20and. 21, and makes instantaneous torque changes in the specimen sets l1,l2 and 24, possible without inducing resonance or inertia loads. Thetorque changes are not through the mass of the gears from one specimenset to the other. The system makes precise control of the torque programmuch more simple, and increases the frequency at which torque can bechanged without having a resonance excitation of the overall system.This makes it possible to more closely duplicate actual field loads onthe specimens being tested.

The torque program can come as a stepped input increase in torque or canbe a varying torque program that quickly changes the torque as desired.The control system of course is utilized in many different controlsequences, and operates using conventional components for obtaining theresults desired.

, What is claimed is:

l. A test stand device comprising means for testing at least tworotating specimens dynamically, first means mechanically connectingfirst ends of said specimens for rotation simultaneously with respect toeach other while eachspecimen is under torque, second means mechanicallyconnecting the second ends of said specimens for rotationsimultaneously, drive means to rotate said specimens, said second meansincluding rotating torque transmitting members, means coupling saidspecimens to the rotating torque transmitting members, said couplingmeans comprising actuators to control torque level between saidspecimens and said rotating torque transmitting members and includingmeans for substantially simultaneously adjusting the actuators to changethe torque carried by each of said specimens without transmitting thetorque change through said first means from one specimen to the other. i

2. The combination as specified in claim 1 wherein said actuator meanscomprise fluid pressure actuator means, servo valve means to control thelevel of torque transmitted by said fluid pressure actuator means, andload cell means sensing the torque level of said specimens to provide acontrol signal for said servo valve means.

3. The combination as specified in claim 1 wherein said first meanscomprises a pair of gears drivably connected together to transmit torquebetween the first ends of said specimens.

4.'The combination as specified in claim 1 wherein there are fourspecimens comprising four shafts, and wherein said shafts are coupled inpairs end to end to form'two pairs of shafts with each pair comprisingtwo shafts in series, and wherein said first means andsecond means areconnected between the pairs of shafts.

5. A test stand device comprising means for simultaneously changing thetorque in a four square test system without subjecting the testspecimens to inertial loads from the connecting drive means comprisingat least one pair of specimens arranged in substantially side by siderelationship, first mechanicaltorque transmitting drive means drivablyconnecting first ends of said specimens, second torque transmittingdrive means drivably connecting second ends of said specimens, saidsecond torque transmitting drive means comprising a pair of rotatingdrive members drivably coupled together and separate fluid pressureactuator means connected between each of said specimens and said drivemembers, said fluid pressure actuator means being operably connected totransmit torque between said specimens and said drive members, servovalve means to control said fluid pressure actuator means wherebychanges in torquein the specimens can be made through said fluidpressure actuator means substantially simultaneously to each of saidspecimens without being transmitted from one specimen to the otherthrough said first mechanical torque transmitting drive means, and meansto rotate said specimens.

6. The combination as specified in claim 5 wherein each of said fluidpressure actuator means comprise rotary actuators, said rotary actuatorshaving first and second elements, one of said elements being connectedto the actuators associated specimen and the other said elements beingconnected to its associated drive member, sensing means to determine theangle between said first and second elements relative to a referenceposition, and control means to provide equal relative deflection of saidfirst and second elements of each of said fluid pressure actuatorsrelative the reference position.

7. The combination as specified in claim 5 wherein said fluid pressureactuators comprise servo valve actuated hydraulic rotary actuators.

8. The combination as specified in claim 7 and hydraulic coupling meansfor transmitting hydraulic fluid under pressure to said actuators whilesaid specimens are rotating.

9. The combination as specified in claim 5 wherein said first torquetransmitting drive means comprise spur gear members drivably engagingeach other, and connected to the respective specimens.

10. The combination as specified in claim 9 and load cell means in eachof said shaft means, and said load cell means being coupled to provide asignal proportional to the torque transmitted by each of the saidspecimens, and means to control the torque transmitted by each of saidfluid pressure actuator means in response to signals from said load cellmeans.

11. The combination as specified in claim 10 and control meansresponsive to said load cell means to maintain the force transmitted bysaid fluid pressure actuator means at a preselected level.

12. In a four square specimen testing device comprising a plurality oftest specimens to be subjected to torque arranged in a series-parallelsystem comprising two sets of specimens, a set of first gear drive meansbetween first ends of said specimens, power means to rotate saidspecimens, wherein the improvement comprises means to transmit torquebetween second ends of said test specimens comprising rotating torquetransmitting drive means and separate rotary hydraulic actuatorsconnected to each of the sets of specimens and being separately andsimultaneously actuable, said hydraulic actuators each including firstand second elements, means to introduce fluid pressure into saidhydraulic actuators while said specimens are rotating, a first of saidelements of each of said hydraulic actuators being connected to onerespective set of specimens and a second element of each of saidhydraulic actuators being connected to the torque transmitting drivemeans for its associated set of specimens, and means to determine theamount of torque being carried by each of said sets of specimens, meanscontrolling said hydraulic actuators to be operable to introduce torquechanges into each of the sets of the specimens independently of the saiddrive connection at the first ends from fluid pressure acting betweenthe first and second elements of that actuator.

1. A test stand device comprising means for testing at least tworotating specimens dynamically, first means mechanically connectingfirst ends of said specimens for rotation simultaneously with respect toeach other while each specimen is under torque, second meansmechanically connecting the second ends of said specimens for rotationsimultaneously, drive means to rotate said specimens, said second meansincluding rotating torque transmitting members, means coupling saidspecimens to the rotating torque transmitting members, said couplingmeans comprising actuators to control torque level between saidspecimens and said rotating torque transmitting members and includingmeans for substantially simultaneously adjusting the actuators to changethe torque carried by each of said specimens without transmitting thetorque change through said first means from one specimen to the other.2. The combination as specified in claim 1 wherein said actuator meanscomprise fluid pressure actuator means, servo valve means to control thelevel of torque transmitted by said fluid pressure actuator means, andload cell means sensing the torque level of said specimens to provide acontrol signal for said servo valve means.
 3. The combination asspecified in claim 1 wherein said first means comprises a pair of gearsdrivably connected together to transmit torque between the first ends ofsaid specimens.
 4. The combination as specified in claim 1 wherein thereare four specimens comprising four shafts, and wherein said shafts arecoupled in pairs end to end to form two pairs of shafts with each paircomprising two shafts in series, and wherein said first means and secondmeans are connected between the pairs of shafts.
 5. A test stand devicecomprising means for simultaneously changing the torque in a four squaretest system without subjecting the test specimens to inertial loads fromthe connecting drive means comprising at least one pair of specimensarranged in substantially side by side relationship, first mechanicaltorque transmitting drive means drivably connecting first ends of saidspecimens, second torque transmitting drive means drivably connectingsecond ends of said specimens, said second torque transmitting drivemeans comprising a pair of rotating drive members drivably coupledtogether and separate fluid pressure actuator means connected betweeneach of said specimens and said drive members, said fluid pressureactuator means being operably connected to transmit torque between saidspecimens and said drive members, servo valve means to control saidfluid pressure actuator means whereby changes in torque in the specimenscan be made through said fluid pressure actuator means substantiallysimultaneously to each of said specimens without being transmitted fromone specimen to the other through said first mechanical torquetransmitting drive means, and means to rotate said specimens.
 6. Thecombination as specified in claim 5 wherein each of said fluid pressureactuator means comprise rotary actuators, said rotary actuators havingfirst and second elements, one of said elements being connected to theactuator''s associated specimen and the other said elements beingconnected to its associated drive member, sensing means to determine theangle between said first and second elements relative to a referenceposition, and control means to provide equal relative deflection of saidfirst and second elements of each of said fluid pressure actuatorsrelative the reference position.
 7. The combination as specified inclaim 5 wherein said fluid pressure actuators comprise servo valveactuated hydraulic rotary actuators.
 8. The combination as specified inclaim 7 and hydraulic coupling means for transmitting hydraulic fluidunder pressure to said actuators while said specimens are rotating. 9.The combination as specified in claim 5 wherein said first torquetransmitting drive means comprise spur gear members drivably engagingeach other, and cOnnected to the respective specimens.
 10. Thecombination as specified in claim 9 and load cell means in each of saidshaft means, and said load cell means being coupled to provide a signalproportional to the torque transmitted by each of the said specimens,and means to control the torque transmitted by each of said fluidpressure actuator means in response to signals from said load cellmeans.
 11. The combination as specified in claim 10 and control meansresponsive to said load cell means to maintain the force transmitted bysaid fluid pressure actuator means at a preselected level.
 12. In a foursquare specimen testing device comprising a plurality of test specimensto be subjected to torque arranged in a series-parallel systemcomprising two sets of specimens, a set of first gear drive meansbetween first ends of said specimens, power means to rotate saidspecimens, wherein the improvement comprises means to transmit torquebetween second ends of said test specimens comprising rotating torquetransmitting drive means and separate rotary hydraulic actuatorsconnected to each of the sets of specimens and being separately andsimultaneously actuable, said hydraulic actuators each including firstand second elements, means to introduce fluid pressure into saidhydraulic actuators while said specimens are rotating, a first of saidelements of each of said hydraulic actuators being connected to onerespective set of specimens and a second element of each of saidhydraulic actuators being connected to the torque transmitting drivemeans for its associated set of specimens, and means to determine theamount of torque being carried by each of said sets of specimens, meanscontrolling said hydraulic actuators to be operable to introduce torquechanges into each of the sets of the specimens independently of the saiddrive connection at the first ends from fluid pressure acting betweenthe first and second elements of that actuator.